Partially fluorinated copolymer based on trifluorostyrene and substituted vinyl compound and ionic conductive polymer membrane formed therefrom

ABSTRACT

A trifluorostyrene and substituted vinyl compound based partially fluorinated copolymer, an ionic conductive polymer membrane including the same, and a fuel cell adopting the ionic conductive polymer membrane, wherein the partially fluorinated copolymer has formula (1):                    
     where each of R 1 , R 2  and R 3  is F, H or CH 3 ; X is a hydroxy group or a trifluoromethyl group; m is an integer greater than zero; n is an integer greater than zero; and p, q and r are zero or integers greater than zero.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a partially fluorinated copolymer basedon a trifluorostyrene and a substituted vinyl compound, and to an ionicconductive polymer membrane formed of the same. More particularly, thepresent invention relates to a partially fluorinated copolymer withtrifluorostyrene units and substituted vinyl compound units, and to anionic conductive polymer membrane, formed of the copolymer, which hasexcellent mechanical properties and a low degree of swelling caused bywater absorption, and to a fuel cell having the ionic conductive polymermembrane.

2. Description of the Related Art

Recently, with the advance of portable electronic devices and wirelesscommunications devices, the need for high performance fuel cells forthese portable devices has increased. In order to improve the efficiencyof fuel cells, a polymer membrane which ensures a high ionicconductivity and reduces the cross-over of fuel, particularly ofmethanol, is needed.

The fuel cell is a power generating system which converts the energygenerated by electrochemical reaction of a fuel and an oxidizing gas toelectrical energy for use. Fuel cells are classified into, for example,fuel cells with a molten carbonate salt electrolyte operable at a hightemperature of 500-700° C., fuel cells with a phosphoric acidelectrolyte operable around 200° C., fuel cells with an alkalielectrolyte operable in a wide range of temperature from roomtemperature to 100° C. or less, fuel cells with a proton exchangemembrane as electrolyte, and fuel cells with a solid electrolyteoperable at a high temperature of 600-1000° C.

Polymer electrolyte fuel cells include the proton exchange membrane fuelcell (PEMFC) using hydrogen gas as fuel, and the direct methanol fuelcell (DMFC) which uses liquid methanol from the anode as direct fuel.

The proton exchange membrane fuel cell (PEMFC), a future clean energysource emerging as a substitute for fossil energy, has high outputdensity and energy conversion efficiency. Also, the PEMFC is workable atroom temperature and is easy to seal and miniaturize, so that it can beextensively used in the fields of pollution-free vehicles, householdpower generating systems, mobile telecommunications, portable powergenerating systems, and medical, military and space equipment.

The PEMFC is a power generator for producing direct current through theelectrochemical reaction of hydrogen and oxygen. The basic structure ofsuch a cell is shown in FIG. 1. Referring to FIG. 1, the PEMFC has aproton exchange membrane 11 interposed between the anode and thecathode.

The proton exchange membrane 11 is formed of a solid polymer electrolytewith a thickness of 20-200 μm. The anode and cathode include supportlayers 14 and 15 for supplying reaction gas, and catalytic layers 12 and13 in which oxidation/reduction of the reaction gas occurs, whichcollectively form a “gas diffusion electrode.” In FIG. 1, referencenumeral 16 represents a current collector.

In the PEMFC having the above structure, with the application ofhydrogen gas as a reaction gas, hydrogen molecules are decomposed intohydrogen ions and electrons by an oxidation reaction in the anode. Thehydrogen ions so produced reach the cathode through the proton exchangemembrane 11.

Meanwhile, in the cathode oxygen molecules take electrons from the anodethrough the membrane and are reduced to oxygen ions by reduction. Theoxygen ions so produced react with hydrogen ions from the anode andproduce water molecules.

As shown in FIG. 1, in the PEMFC, the catalytic layers 12 and 13 of thegas diffusion electrode are formed over the support layers 14 and 15,respectively. The support layers 14 and 15 are formed of carbon cloth orcarbon paper. The surface of the support layers 14 and 15 are treated soas to allow easy passing of reaction gas, of water to the proton ionexchange membrane 11, and of water obtained as the reaction product.

On the other hand, the DMFC has the same structure as the PEMFC, butuses liquid methanol, instead of hydrogen, as a reaction fuel. As theliquid methanol is supplied to the anode, an oxidation reaction occursin the presence of a catalyst, so that hydrogen ions, electrons andcarbon dioxide are generated. The DMFC has poor cell efficiency comparedwith the PEMFC because of lower catalytic activities of the anodicfuels. However, use of liquid fuel makes its application to potableelectronic devices easier.

The previously mentioned fuel cells usually employ an ionic conductivepolymer membrane as the proton exchange membrane disposed between theanode and the cathode. The ionic conductive polymer membrane, as anelectrolyte of the fuel cell, serves to transfer hydrogen ions from theanode to the cathode, and prevents the fuels for each of the anode andcathode from being mixing with each other. In addition, the ionicconductive polymer membrane is formed of a polymer membrane withsulfonyl groups as side chains. Because the polymer membrane containswater, a sulfonic acid group of the polymer electrolyte is dissociatedin the water medium so that the sulfonyl group is produced with ionicconductivity.

The ionic conductive polymer membrane should have the followingcharacteristics: a high ionic conductivity, electrochemical stability,mechanical properties suitable as a membrane, thermal stability atworking temperature, easy processing into a thin film for reducedresistance, low cost and low degree of swelling caused by liquidabsorption, etc.

The most widely known ionic conductive polymer membrane has apolytetrafluoroethylene backbone having sulfonyl group as side chains.However, this polymer membrane is of little practical use due to itshigh manufacturing cost and complicated manufacturing process. To solvethese problems, an ionic conductive polymer membrane formed ofpolytrifluorostyrene, a partially fluorinated polymer, has beensuggested in U.S. Pat. Nos. 5,422,411; 5,498,639; 5,602,185; 5,684,192;5,773,480; and 5,834,523. However, the ionic conductive polymer based onsulfonated polytrifluorostyrene is known to be very brittle and thus hasdifficulty in practical use. For this reason, to enhance the mechanicalstrength of the polymer membrane, there has been used a copolymer oftrifluorostyrene, and a polymer which is able to be polymerized withtriflurostyrene, for example, a monomer containing fluorine with a longside chain, such as heptadecafluorodecyl acrylate,heptadecafluorodecene, hydroxypropyl methacrylate, hydroxybutyl acrylateand hydroxyethyl methacrylate.

When the ionic conductive polymer membrane is applied to a fuel cell,the polymer membrane absorbs water and serves as a medium which allowshydrogen ions to pass. As the polymer membrane absorbs water, thethickness and the area of the polymer membrane varies by swelling.However, if the degree of the swelling is excessive, due to thedifference between the dry state and the full water absorption state,manufacturing a fule cell with the polymer membrane becomes difficult.

SUMMARY OF THE INVENTION

It is a first feature of the present invention to provide a copolymerbased on trifluorostyrene and a substituted vinyl compound.

A second feature of the present invention is to provide an ionicconductive polymer membrane formed of the copolymer, which has a lowdegree of swelling caused by water absorption and excellent mechanicalproperties.

A third feature of the present invention is to provide a fuel cell withimproved efficiency, which employs the ionic conductive polymermembrane.

In accordance with one aspect of the present invention, there isprovided a partially fluorinated copolymer having formula (1) below,comprising trifluorostyrene units and substituted vinyl compound units:

wherein each of R₁, R₂ and R₃ independently is selected from the groupconsisting of F, H and CH₃; X is a hydroxy group or a trifluoromethylgroup; m is an integer greater than zero; n is an integer greater thanzero; and p, q and r are zero or integers greater than zero.

In accordance with another aspect of the present invention, there isprovided an ionic conductive polymer membrane comprising a partiallyfluorinated copolymer having formula (1) with trifluorostyrene units andsubstituted vinyl compound units:

wherein each of R₁, R₂ and R₃ independently is selected from the groupconsisting of F, H and CH₃; X is a hydroxy group or a trifluoromethylgroup; m is an integer greater than zero; n is an integer greater thanzero; and p, q and r are zero or integers greater than zero.

According to a further aspect of the present invention, there isprovided a fuel cell comprising an ionic conductive layer that comprisesa partially fluorinated copolymer having formula (1) withtrifluorostyrene units and substituted vinyl compound units:

wherein each of R₁, R₂ and R₃ independently is selected from the groupconsisting of F, H and CH₃; X is a hydroxy group or a trifluoromethylgroup; m is an integer greater than zero; n is an integer greater thanzero; and p, q and r are zero or integers greater than zero.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail preferred embodimentsthereof with reference to the attached drawings in which:

FIG. 1 illustrates the structure of a conventional fuel cell adopting aproton exchange membrane;

FIG. 2 is a graph illustrating the variation in ionic conductivity ofthe inventive ionic conductive polymer membrane of Synthesis Example 1with respect to temperature;

FIG. 3 is a graph illustrating the variation in cell potential of theproton exchange membrane fuel cell (PEMFC) manufactured in Example 1with respect to current density; and

FIG. 4 is a graph illustrating the variation in cell potential of theinventive direct methanol fuel cell (DMFC) manufactured in Example 2with respect to current density.

DETAILED DESCRIPTION OF THE INVENTION

Priority Korean Patent Application Serial No. 00-37394, filed Jun. 30,2000, is hereby incorporated in its entirety by reference.

A partially fluorinated copolymer having formula (1) above according tothe present invention is derived by polymerizing a trifluorostyrenemonomer and a substituted vinyl compound monomer, and sulfonating thepolymerized product. The trifluorostyrene monomer can include, withoutlimitation, α, β, β-trifluorostyrene. The substituted vinyl compoundmonomer can include, without limitation, heptadecafluorodecylmethacrylate, heptadecafluorodecene and heptadecafluoro-decyl acrylate.

The polymerization reaction of the trifluorostyrene monomer and thesubstituted vinyl compound monomer will be described in greater detail.In the present invention, the polymerization reaction preferably isperformed by an emulsion polymerization method. A polymerizationinitiator, for example, potassium persulfate, can be added for thepolymerization. Dodecylamine hydrochloride or sodium stearate (soap) canbe used as an emulsifier.

When the polymerization of the trifluorostyrene monomer and thesubstituted vinyl compound monomer is completed, an emulsifier used inthe emulsion polymerization is removed and the copolymer is subjected tosulfonation with a sulfonation agent such as chlorosulfonic acid. Thedegree of sulfonation can be varied by adjusting the amount of thesulfonation agent. After the sulfonation is completed, an ionicconductive polymer membrane for fuel cells is obtained by casting asolution containing the resultant sulfonated copolymer or hot pressingthe resultant sulfonated copolymer.

In formula (1) above, preferably, m is an integer from 1 to 50, n is aninteger from 1 to 50, p is zero or an integer from 1 to 12, and q iszero or an integer from 1 to 12.

Preferably, the partially fluorinated copolymer having formula (1) abovehas a weight average molecular weight of about 30,000 to about 500,000.If the weight average molecular weight of the partially fluorinatedcopolymer is less than about 30,000, formation of a film is difficult.If the weight average molecular weight of the partially fluorinatedcopolymer exceeds about 500,000, the solubility of the copolymer inorganic solvents is poor.

Specific embodiments of the partially fluorinated copolymer havingformula (1) include the compounds having formulas (2) through (5):

where m is an integer greater than zero; and n is an integer greaterthan zero. Preferably, in formula (1) through (5), m is an integer from1 to 50; and n is an integer from 1 to 50.

The copolymer having formula (1) above can be partially crosslinked witha crosslinking agent, which is a multi-functional compound having two ormore unsaturated groups per molecule. The crosslinking reaction takesplace when a mixture of the copolymer having formula (1) and thecrosslinking agent is subjected to casting or hot pressing to form apolymer membrane. Note that when the degree of sulfonation of thecopolymer represented by formula 1 is high, the copolymer of formula 1is partially self-crosslinked.

Useful crosslinking agents include, without limitation, divinyl benzene,diallyl ether, trially ether, diglycidyl ether, ethylene glycoldimethacrylate, and mixtures of these compounds. When partiallycrosslinking the copolymer having formula (1) with a crosslinking agent,ionic conductivity slightly decreases and the degree of swelling in thewet state is reduced. Thus, a difference in volumes of the polymermembrane in the dry and wet states is decreased.

Exemplary crosslinked compounds are give below. The copolymerillustrated on the right is derived when divinyl benzene is used as thecrosslinking agent. The copolymer illustrated on the left is obtained asa result of self-crosslinking of a copolymer with a high degree ofsulfonation.

where m is an integer greater than zero; n is an integer greater thanzero; and p and r are zero or integers greater than zero. Preferably, mis an integer from 1 to 50, n is an integer from 1 to 50, p is zero oran integer from 1 to 12, and q is zero or an integer from 1 to 12.

On the other hand, in manufacturing a fuel cell according to the presentinvention, a catalytic layer is formed over both sides of the ionicconductive polymer membrane formed of the copolymer having formula (1),and bonded with each electrode support layer, so that a membrane andelectrode assembly (MEA) is completed. Next, a current collector isattached to both sides of the MEA, thereby resulting in a complete fuelcell.

The present invention will be described in greater detail by means ofthe following examples. The following examples are for illustrativepurposes and are not intended to limit the scope of the invention.

Synthesis Example 1

80 g α,β,β-trifluorostyrene, 15 g heptadecafluorodecyl methacrylate, 600ml deionized water and 9.5 g dodecylamine hydrochloride were placed intoa 4-necked flask equipped with a mechanical stirrer and mixed. Duringthe mixing process, the flask was conditioned in a nitrogen atmosphere.Next, the flask containing the reactants was purged with nitrogen gasfor 30 minutes, and was then kept at 55±1° C. A solution obtained bydissolving 0.35 g potassium persulfate in 5 g deionized water wasinjected into the reaction mixture with a syringe. The mixture was leftat 55±1° C. for 72 hours for reaction.

30 g sodium chloride and 50 g ice were added to the reaction mixture andfiltered in a vacuum to obtain copolymer powder. The resultant copolymerpowder was washed with deionized water and then with cold methanol. Thewashed copolymer powder was dried at room temperature for a day, anddried again in a vacuum oven at room temperature for 5-6 hours.

4.78 g of the resultant copolymer was completely dissolved in 300 mlchloroform, and 2 cc chlorosulfonic acid was added to the solution witha syringe. The mixture was reacted at 65° C. for 3 hours, and cooled toroom temperature. Next, the solvent was decanted from the reactionproduct. Then, methanol was added to the resultant product andevaporated in a vacuum to remove the remaining solvent, therebyresulting in a sulfonated copolymer having formula (2) above. As for thesulfonated copolymer so obtained, m and n of formula (2) were 9 and 2,respectively. The weight average molecular weight of the resultantcopolymer was 95,000.

IR(KBr, cm⁻¹): v 2900, 1730, 1300, 1100-1400

Synthesis Example 2

50 g α,β,β-trifluorostyrene, 10 g heptadecafluorodecyl methacrylate, 400ml deionized water and 5.0 g dodecylamine hydrochloride were placed intoa 4-necked flask equipped with a mechanical stirrer and mixed. Duringthe mixing process, the flask was conditioned in a nitrogen atmosphere.Next, the flask containing the reactants was purged with nitrogen gasfor 30 minutes, and was kept at 55±1° C. A solution obtained bydissolving 0.25 g potassium persulfate in 5 g deionized water wasinjected into the reaction mixture with a syringe. The mixture was leftat 55±1° C. for 72 hours for reaction.

25 g sodium chloride and 50 g ice were added to the reaction mixture andfiltered in a vacuum to obtain copolymer powder. The resultant copolymerpowder was washed with deionized water and then with cold methanol. Thewashed copolymer powder was dried at room temperature for a day, anddried again in a vacuum oven at room temperature for 5-6 hours.

6 g of the resultant copolymer were completely dissolved in 300 mlchloroform, and 1.2 cc chlorosulfonic acid was added to the solutionwith a syringe. The mixture was reacted at 65° C. for 3 hours, andcooled to room temperature. Next, the solvent was decanted from thereaction product. Then, methanol was added to the resultant product andevaporated in a vacuum to remove the remaining solvent, therebyresulting in a sulfonated copolymer having formula (3) above. As for thesulfonated copolymer so obtained, m and n of formula (3) were 8 and 2,respectively. The weight average molecular weight of the resultantcopolymer was 80,700.

IR(KBr, cm⁻¹): v 3000, 1730, 1300, 1100-1400

Synthesis Example 3

20 g α,β,β-trifluorostyrene, 5 g heptadecafluorodecene, 400 ml deionizedwater and 2.9 g dodecylamine hydrochloride were placed into a 4-neckedflask equipped with a mechanical stirrer and sufficiently mixed. Duringthe mixing process, the flask was conditioned in a nitrogen atmosphere.Next, the flask containing the reactants was purged with nitrogen gasfor 30 minutes, and was kept at 55±1° C. While maintaining thetemperature of the reaction mixture at the selected temperature, asolution obtained by dissolving 0.2 g potassium persulfate in 5 gdeionized water was injected into the reaction mixture with a syringe.The mixture was left at 55±1° C. for 72 hours for reaction.

After the reaction was completed, 50 g ice and 25 g sodium chloride wereadded to the reaction mixture and filtered in a vacuum to obtaincopolymer powder. The resultant copolymer powder was washed withdeionized water and then with cold methanol. The washed copolymer powderwas dried at room temperature for a day, and dried again in a vacuumoven at room temperature for 5-6 hours.

6 g of the resultant copolymer was dissolved in 300 ml chloroform, and1.2 cc chlorosulfonic acid was dropwise added to the solution with asyringe. The mixture was reacted at 65° C. for 3 hours, and cooled toroom temperature. Next, the solvent was decanted from the reactionproduct. Then, methanol was added to the resultant product andevaporated in a vacuum to remove the remaining solvent, therebyresulting in a sulfonated copolymer having formula (4) above. As for thesulfonated copolymer so obtained, m and n of formula (4) were 13 and 3,respectively. The weight average molecular weight of the resultantcopolymer was 82,500.

IR(KBr, cm⁻¹): v 3000, 1300,1100-1400

Synthesis Example 4

90 g α,β,β-trifluorostyrene, 30 g hydroxypropyl methacrylate, 500 mldeionized water and 11.8 g dodecylamine hydrochloride were placed into a4-necked flask equipped with a mechanical stirrer and sufficientlymixed. During the mixing process, the flask was conditioned in anitrogen atmosphere.

Next, the flask containing the reactants was purged with nitrogen gasfor 30 minutes, and was kept at 55±1° C. While maintaining thetemperature of the reaction mixture at the selected temperature, asolution obtained by dissolving 0.445 g potassium persulfate in 5 gdeionized water was injected into the reaction mixture with a syringe.The mixture was left at 55±1° C. for 72 hours for reaction.

After the reaction was completed, 30 g sodium chloride and 50 g ice wereadded to the reaction mixture and filtered in a vacuum to obtaincopolymer powder. The resultant copolymer powder was washed withdeionized water and then with cold methanol. The washed copolymer powderwas dried at room temperature for a day, and dried again in a vacuumoven at room temperature for 5-6 hours.

8.5 g of the resultant copolymer was dissolved in 500 ml chloroform, and1.6 cc chlorosulfonic acid was dropwise added to the solution with asyringe. The mixture was reacted at 68° for 3 hours, and cooled to roomtemperature. Next, the solvent was decanted from the reaction product.Then, methanol was added to the resultant product and evaporated in avacuum to remove the remaining solvent, thereby resulting in asulfonated copolymer having formula (5) above. As for the obtainedsulfonated copolymer, m and n of formula (5) were 15 and 14,respectively. The weight average molecular weight of the resultantcopolymer was 93,000.

IR(KBr, cm⁻¹): v 3600, 2900-2700, 1730

Ionic conductive polymer membranes were manufactured by hot pressing thesulfonated copolymers derived in Synthesis Examples 1 through 4 at atemperature of 100° C. and a pressure of 23 Mton for 5 minutes.Variations in ionic conductivity of the obtained ionic conductivepolymer membranes with respect to temperature were measured.

FIG. 2 illustrates the ionic conductivity of the ionic conductivepolymer membrane formed of the sulfonated copolymer of Synthesis Example1 with respect to temperature. As shown in FIG. 2, the ionicconductivity of the ionic conductive polymer membrane is 10⁻¹ S/cm ormore in the range of 30-70° C., which is satisfactory for use as aproton exchange membrane for fuel cells.

As for the ionic conductive polymer membranes manufactured using thepolymers of Synthesis Examples 2 through 4, the ionic conductiveproperties show a tendency similar to those of the ionic conductivepolymer membrane for Synthesis Example 1.

Synthesis Example 5

600 ml deionized water, 11.6 g dodecylamine hydrochloride, and 100 gα,β,β-trifluorostyrene were placed into a 4-necked flask equipped with amechanical stirrer and sufficiently mixed with the stirrer in a nitrogenatmosphere.

Next, the flask containing the reactants was purged with nitrogen gasfor 30 minutes, and was kept at 55±1° C. After dissolving 0.8 gpotassium persulfate in deionized water, the solution was injected intothe reaction mixture with a syringe.

The mixture was left for 48 hours for reaction. After the reaction wascompleted, 50 g ice and 100 g sodium chloride were added to the reactionmixture and filtered in a vacuum to obtain copolymer powder. Theresultant copolymer powder was washed with deionized water and then withcold methanol. The washed copolymer powder was dried at room temperaturefor a day, and dried again in a vacuum oven at room temperature for 5-6hours. The resultant copolymer has formula (1) above, where m=4.

Example 1

An ionic conductive polymer membrane was manufactured by hot pressingthe sulfonated copolymer obtained in Synthesis Example 1 at atemperature of 100° C. and a pressure of 23 Mton for 5 minutes.

A catalytic layer was formed on both sides of the ionic conductivepolymer membrane, and bonded with each electrode support layer, so thata membrane and electrode assembly (MEA) was manufactured. A currentcollector was attached to both sides of the completed MEA, therebyresulting in a complete proton exchange membrane fuel cell (PEMFC).

Example 2

A PEMFC was manufactured in the same manner as in Example 1, except thatthe sulfonated copolymer of Synthesis Example 2 was used instead of thesulfonated copolymer of Synthesis Example 1.

Example 3

An ionic conductive polymer membrane was manufactured by hot pressingthe sulfonated copolymer obtained in Synthesis Example 1 at atemperature of 100° C. and a pressure of 23 Mton for 5 minutes.

A catalytic layer was formed on both sides of the ionic conductivepolymer membrane, and bonded with each electrode support layer, so thata membrane and electrode assembly (MEA) was manufactured. A currentcollector was attached to both sides of the completed MEA, therebyresulting in a complete direct methanol fuel cell (DMFC).

Performance of the fuel cells manufactured in Examples 1 through 3 wasevaluated. The results are shown in FIGS. 3 and 4. FIGS. 3 and 4 showvariations in cell potential of the PEMFC of Example 1 and the DMFC ofExample 3, respectively, with respect to current density. As shown inFIGS. 3 and 4, the PEMFC and DMFC which adopt the ionic conductive layerformed of the copolymer of Synthesis Example 1 have good cell potentialcharacteristics at a temperature of 70-80° C. Here, the cell potentialcharacteristic of the PEMFC and DMFC was measured by measuring a voltagelevel with application of current while fuel is supplied to the cell.The cell potential characteristic is evaluated as excellent when thevoltage level increases with application of a constant current.

The copolymer having formula (1) according to the present inventionincludes trifluorostyrene units and substituted vinyl compound units,which can be partially crosslinked. Ionic conductive polymer membranescan be manufactured using the copolymer at low cost, with excellentmechanical properties. When a partially crosslinked copolymer is used,the degree of swelling of the resulting polymer membrane and fuelcrossover can be reduced compared with a conventional polymer. Theefficiency of fuel cells can be improved by applying thepolytrifluorostyrene-based ionic conductive copolymer membrane.

While this invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade thereto without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. An ionic conductive polymer membrane comprising a partially fluorinated copolymer having formula (1):

wherein each of R₁, R₂ and R₃ independently is selected from the group consisting of H and CH₃; X is a hydroxy group or a trifluoromethyl group; m is an integer greater than zero; n is an integer greater than zero; and p, q and r are zero or integers greater than zero.
 2. The ionic conductive polymer membrane of claim 1, wherein, in formula (1), m is an integer from 1 to 50, n is an integer from 1 to 50; p is zero or an integer from 1 to 12; and q is zero or an integer from 1 to
 12. 3. The ionic conductive polymer membrane of claim 1, wherein the partially fluorinated copolymer having formula (1) is a compound having one selected from formulas (2) to (5):

where m is an integer from 1 to 50; and n is an integer from 1 to
 50. 4. The ionic conductive polymer membrane of claim 1, wherein the partially fluorinated copolymer having formula (1) has a weight average molecular weight of about 30,000 to about 500,000.
 5. The ionic conductive polymer membrane of claim 1, wherein the partially fluorinated copolymer is partially crosslinked using a crosslinking agent.
 6. The ionic conductive polymer membrane of claim 5, wherein the crosslinking agent comprises at least one selected from the group consisting of divinyl benzene, diallyl ether, triallyl ether, diglycidyl ether and ethylene glycol dimethacrylate. 